This invention relates to the field of vehicle suspension systems and to the augmentation of vehicle suspension systems to enable heavy loading. Specifically, this invention relates to a new and useful attachment which provides for adjustable fortification of standard leaf spring suspension systems for heavy loading applications.
Not applicable.
This invention was not developed in conjunction with any Federally sponsored contract.
Not applicable.
The use of work vehicles continues to increase as best evidenced by continuing growth of pickup truck sales each year. Despite the continuing urbanization of America, the use of work vehicles commonly associated with rural populations continues to increase. Annual sales of half, three quarter, and one ton pickup trucks has never been higher. Pickup trucks are now commonly used in roles once reserved for passenger vehicles, ie., taking kids to school, going to the grocery store, driving to and from work, etc. However, these same xe2x80x9curbanizedxe2x80x9d work vehicles will often be used for the occasional work task and will be subjected to periodic heavy loading, often exceeding the design limits of the vehicle.
Since 1988 and the advent of xe2x80x9csport utility vehiclesxe2x80x9d (SUV), many car and truck manufacturers have used the same frame and suspension systems for their SUV""s as used in their light and heavy duty pickup trucks. In many cases, the main difference between an SUV and a corresponding pickup truck is the body and interior trim. SUV""s have become popular family vehicles, serving as a means to transport family members to work and school during the week, and serving as a hauling vehicle during the weekends for home projects. Additionally, some xe2x80x9cmini-vansxe2x80x9d are based upon a truck frame and suspension system, as well.
For the remainder of this disclosure, the term xe2x80x9cpickup truckxe2x80x9d or xe2x80x9ctruckxe2x80x9d will be used to collectively refer to all vehicles based upon a pickup truck chassis.
As thoroughly described in the references included herein, an overloaded pickup truck whether carrying the load in the bed or on a trailer, will tend to drop in the rear and rise in the front. This indicates a drastically uneven weight distribution wherein the rear wheels carry most of the load, thus potentially compromising the driving characteristics, handling, and even safety of the vehicle.
U.S. Pat. No. 4,671,535 to Hanson, et al. shows an overload mechanism that includes and abutment structure rigidly mounted to the vehicle frame that, when engaged, contacts the leaf spring in a fixed location. This not only limits the travel of the leaf spring, but also acts to redistribute more of the load to the front wheels.
U.S. Pat. No. 5,172,930 to Boye et al. shows an overload mechanism basically very similar to that disclosed in the Hanson patent except the Boye apparatus is remotely engageable. This mechanism also limits the travel of the rear leaf springs and further acts to redistribute more of the load to the front wheels.
There are known devices which mount to a vehicle frame and engage the rear leaf springs in a fixed position. Each of the above referenced patents disclose abutment mechanisms that are relatively simple, mount between the rear axle and rear bumper, and provide improved weight distribution during overload conditions by effectively lengthening the vehicle wheelbase. The known devices also share the common shortfall that each is effectively non-adjustable. Once it is mounted to the frame, it will always contact the leaf spring in the same location, thereby providing a fixed limit to leaf spring travel. These mechanisms effectively provide a fixed amount of reinforcement.
The magnitude to which a vehicle is overloaded will likely vary greatly from load to load-such that one level of reinforcement is not adequate under many real loading conditions. For example, a vehicle used to pull a trailer one weekend might well be used to haul bags of cement the following weekend, then bales of hay the next. In another example, the inventor""s recently issued U.S. Pat. No. 6,148,928 discloses a three point hitch system for mounting to and use with a pick up truck. Loadings applied during the use of this device will vary from application to application, thus the amount of suspension reinforcement needed will vary accordingly.
Therefor, there exits a need for a device which provides an adjustable amount of reinforcement for the rear suspension of Pickup trucks, SUV""s and minivans. Additionally, there exists a need in the art for this system to be reliable, easily adjustable, and cost effective for mass production.
The system and method of the invention provide an apparatus that, when mounted to a vehicle frame and properly engaged, provides reinforcement to standard leaf spring suspension in a manner that is easily adjustable, and flexible, not rigid, thus providing both improved weight distribution while allowing for additional vertical travel of the suspension system during periods of extreme shock loading such as when an overloaded vehicle might pass over a large pot hole.
The apparatus mounts to the vehicle frame at a location behind the rear axle between the rear axle and rear attachment point of the leaf spring. The apparatus is both vertically and horizontally adjustable and provides an adjustable amount of reinforcement, thus allowing the operator the match the amount of reinforcement to the load.